/* vi: set sw=4 ts=4: */ /* * Mini weak password checker implementation for busybox * * Copyright (C) 2006 Tito Ragusa <farmatito@tiscali.it> * * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. */ /* A good password: 1) should contain at least six characters (man passwd); 2) empty passwords are not permitted; 3) should contain a mix of four different types of characters upper case letters, lower case letters, numbers, special characters such as !@#$%^&*,;". This password types should not be permitted: a) pure numbers: birthdates, social security number, license plate, phone numbers; b) words and all letters only passwords (uppercase, lowercase or mixed) as palindromes, consecutive or repetitive letters or adjacent letters on your keyboard; c) username, real name, company name or (e-mail?) address in any form (as-is, reversed, capitalized, doubled, etc.). (we can check only against username, gecos and hostname) d) common and obvious letter-number replacements (e.g. replace the letter O with number 0) such as "M1cr0$0ft" or "P@ssw0rd" (CAVEAT: we cannot check for them without the use of a dictionary). For each missing type of characters an increase of password length is requested. If user is root we warn only. CAVEAT: some older versions of crypt() truncates passwords to 8 chars, so that aaaaaaaa1Q$ is equal to aaaaaaaa making it possible to fool some of our checks. We don't test for this special case as newer versions of crypt do not truncate passwords. */ #include "libbb.h" static int string_checker_helper(const char *p1, const char *p2) __attribute__ ((__pure__)); static int string_checker_helper(const char *p1, const char *p2) { /* as-is or capitalized */ if (strcasecmp(p1, p2) == 0 /* as sub-string */ || strcasestr(p2, p1) != NULL /* invert in case haystack is shorter than needle */ || strcasestr(p1, p2) != NULL) return 1; return 0; } static int string_checker(const char *p1, const char *p2) { int size; /* check string */ int ret = string_checker_helper(p1, p2); /* Make our own copy */ char *p = xstrdup(p1); /* reverse string */ size = strlen(p); while (size--) { *p = p1[size]; p++; } /* restore pointer */ p -= strlen(p1); /* check reversed string */ ret |= string_checker_helper(p, p2); /* clean up */ memset(p, 0, strlen(p1)); free(p); return ret; } #define LOWERCASE 1 #define UPPERCASE 2 #define NUMBERS 4 #define SPECIAL 8 static const char *obscure_msg(const char *old_p, const char *new_p, const struct passwd *pw) { int i; int c; int length; int mixed = 0; /* Add 2 for each type of characters to the minlen of password */ int size = CONFIG_PASSWORD_MINLEN + 8; const char *p; char *hostname; /* size */ if (!new_p || (length = strlen(new_p)) < CONFIG_PASSWORD_MINLEN) return "too short"; /* no username as-is, as sub-string, reversed, capitalized, doubled */ if (string_checker(new_p, pw->pw_name)) { return "similar to username"; } /* no gecos as-is, as sub-string, reversed, capitalized, doubled */ if (*pw->pw_gecos && string_checker(new_p, pw->pw_gecos)) { return "similar to gecos"; } /* hostname as-is, as sub-string, reversed, capitalized, doubled */ hostname = safe_gethostname(); i = string_checker(new_p, hostname); free(hostname); if (i) return "similar to hostname"; /* Should / Must contain a mix of: */ for (i = 0; i < length; i++) { if (islower(new_p[i])) { /* a-z */ mixed |= LOWERCASE; } else if (isupper(new_p[i])) { /* A-Z */ mixed |= UPPERCASE; } else if (isdigit(new_p[i])) { /* 0-9 */ mixed |= NUMBERS; } else { /* special characters */ mixed |= SPECIAL; } /* More than 50% similar characters ? */ c = 0; p = new_p; while (1) { p = strchr(p, new_p[i]); if (p == NULL) { break; } c++; if (!++p) { break; /* move past the matched char if possible */ } } if (c >= (length / 2)) { return "too many similar characters"; } } for (i=0; i<4; i++) if (mixed & (1<<i)) size -= 2; if (length < size) return "too weak"; if (old_p && old_p[0] != '\0') { /* check vs. old password */ if (string_checker(new_p, old_p)) { return "similar to old password"; } } return NULL; } int FAST_FUNC obscure(const char *old, const char *newval, const struct passwd *pw) { const char *msg; msg = obscure_msg(old, newval, pw); if (msg) { printf("Bad password: %s\n", msg); return 1; } return 0; }